Differences between cytoplasmic and nuclear forms of the androgen receptor will be explored with respect to subunit forms, charge and androgen binding properties, nuclear uptake and intranuclear binding. It will be established whether organ differences in subunit forms of cytoplasmic and nuclear androgen receptors reflect organ specific mechanisms regulating nuclear uptake or binding. Studies on testosterone-and dihydrotestosterone-bound receptors will be carried out to discover how these androgens affect receptor interactions within the nucleus. The role of the nuclear membrane in receptor-androgen uptake will be of particular interest. Also, we will apply new approaches to fractionating nuclei in search for receptor interaction sites. The mechanisms of androgen and FSH control over Sertoli cell function will be studied in vivo using at least two molecular probes. Similar studies will be carried out on the epididymis using acidic epidiymal glycoproteins which appear useful in delineating hormonal mechanisms of other cell types in these tissues as well. Proteins will be purified and used to develop immunological methods for sensitve quantitation of changes in their concentrations in response to hormonal changes. In differentiating the effects of steroids and peptide hormones on Sertoli cells, we will selectively remove only FSH or LH and androgen from intact rats by injecting specific antisera. Attempts will be made to determine whether androgen enhancement of FSH action is mediated by a cyclic nucleotide related step or a more general effect of androgen on the protein synthesizing machinery of the Sertoli cell.